I like the red BG! A couple of things - Iightening the eye would improve the whole image, maybe even adding a tiny eye catchlight! (too bad the head wasn't turned up a little). I would like to see more space on the right, the tail is very close to the edge. Nice pose!
Paul
That brick wall really compliments the color and detail of the mocker. A very sharp image. A head turn sure would have been nice....but sometimes they just have a mind of their own. Perhaps you'll have more chances. I have a couple of mockers that come to my window at school as I feed them raisins. They appear as soon as the light goes on in the morning. If I get busy and don't feed them immediately they've been known to peck on the window to remind me.
THe perch and the BG are used well here to show how close they live among us. The flower is a distraction and a head turn towards you would make the image more intimate - you are looking for eye contact with the bird.
That deep red brick bg is really awesome. I also like the splash of color in the leaves at upper left. I bit of a head turn toward the camera would be nice.